Memory - Multi-Store Model Flashcards
What is memory?
It is the process of retaining and recalling information about events that have happened in the past.
What are the main two types of memory?
Short term memory -
- Your memory for immediate events, which disappears if not rehearsed
Long term memory -
- Your memory for events that have happened in the past anywhere between 2 minutes and 100 years - it is a permanent memory store
- There is also sensory register which stores a huge amount of information from our senses for a very brief amount of time (around half a second)
Two main types of coding
Acoustic - a memory linked to sounds / formatted information into sounds
Semantic - a memory linked to facts / information is stored as the factual meaning of the event
Memory definitions
Capacity - The amount of information that can be stored
Duration - The length of time information can be held in the memory store
Coding - The format in which information is stored in the memory stores; it’s the process of converting information from one format to another
What is the STM?
The short term memory temporarily stores information received from the sensory register and it is an active and changing memory system as it contains information currently being thought about.
What is the LTM?
This involves storing memory over a long period of time, with any information being stored for more than 30 seconds counting as LTM. All information received here goes through the sensory register and STM first after undergoing different forms of processing.
Strong LTM’s can be easily recalled, whereas weaker ones need more prompting - LTMs are not passive, as they merge and change with other LTMs over time, which is why memories are necessarily constant and accurate. The process of shaping and storing LTM is also spread through multiple brain regions.
Capacity in the STM
- Limited capacity that holds a small amount of information from the SR that has been paid attention too
- Chunking can help to improve the capacity by increasing the size of units of information in storage by giving them collective meaning
- It was said to have a capacity of about 5-9 items by Jacobs and Miller, with an average of 7 items and a minimum of 4
- However, there may be individual differences in STM capacity, as seen by Daneman and Carpenter (1980) who noticed that capacity varied between 5-20 items between those who have advanced and poor reading comprehension
- Evaluation - other factors such as age and practice influence STM capacity and nowadays STM limitations are mostly due to processing limitations associated with attention
Capacity in the STM - Jacobs (1887)
- Developed a technique to measure digit span, where the researcher gives 4 digits and then the participant is asked to recall these in the correct order out loud
- If this is correct, the researcher reads out 5 digits and so on until the participant cannot recall the order correctly, determining the individual’s digit span
- Jacobs found that the mean span for digits across all participants was 9.3 items, and the mean span for letters was 7.3
Evaluation - the study was conducted a long time ago, and early psychological research often lacked adequate control, and so some participants may have been distracted during testing and therefore didn’t perform as well as they might
- This would mean results might not be valid because there were confounding variables that were not controlled, but these results have been supported by other studies, improving the validity of results
Capacity in the STM - Miller (1956), Cowan (2001) and Simon (1974)
Miller (1956) -
- From a review of psychological research, he found that capacity / span of human memory is about 7 items, plus or minus 2, and people cope well with counting 7 flashing dots but not much more, which is generalised to digits, numbers and words
- He noted that 5 words can be recalled as well as 5 letters, and this is achieved by chunking, grouping sets of letters or digits into units or chunks
Cowan (2001) -
- Noted that Miller may have overestimated the capacity of STM, as he reviewed other research and concluded that the capacity of STM was only about 4 chunks. This suggests that the lower end of Miller’s estimate (5 items) is more appropriate as an estimation of capacity than 7 items
Simon (1974) -
- Although STM capacity should be measured in terms of chunks, this varies with the type of material being recalled and the amount of information contained within the chunks
Capacity in the LTM
- The potential capacity of the LTM is unlimited; information can be lost due to decay and interference, but such losses don’t occur due to limitation of capacity
- Anokhin (1973) estimated that the number of possible neuronal connections in the human brain is 1 followed by 10.5 million kilometres of noughts, and so concluded that ‘no human yet exists who can use all the potential of their brain’ and this suggests that the capacity of LTM is limitless
- Wagenaar (1986) created a diary of 2,400 events over 6 years and tested himself in his event recall rather than date recall, and found excellent recall, suggesting that LTM capacity is extremely large
Evaluations -
- Anokhin; estimates are not certain
- Wagenaar - diary entries are case studies and are not representative of the general population; there are also issues of researcher bias from self-testing
- The capacity of LTM is assumed to be limitless, as research cannot determine a limitless capacity (neither proven or disproven)
- There may be an evolutionary basis to LTM; animal studies, like those of Fagot & Cook (1996) show that pigeons can memorise 1,200 picture response associations; Baboons still hadn’t reached their capacity after 3 years of training, memorising 5,000 associations
- This suggests that an enlarged memory capacity has a survival mechanism which has been acted upon through natural selection
Duration of the STM
- The amount of time information remains in the STM without being lost is a maximum of 30 seconds, which can be extended through rehearsal of information, which if done consistently enough results in a transfer of the information to the LTM, where it will become more of a long-lasting feature - Peterson and Peterson; 18 seconds when rehearsal is blocked
Evaluation -
- Reitman (1974) suggested the brief duration of STM is due to displacement; as new information comes into STM it pushes out existing information due to its limited capacity
- There is little in the way of research evidence considering the STM duration of other forms of stimuli, like visual images
Duration of the STM - Peterson and Peterson (1959)
Aim -> To investigate the duration of STM and provide empirical evidence for the MSM
Procedure -> A lab experiment was conducted in which 24 undergraduate students took part in 8 trials. On each trial, they were given a consonant syllable or trigram (three consonants) and a three digit number. The student was then asked to count backwards from the number in either 3s or 4s until told to stop, and this was to prevent rehearsal of the consonant syllable. On each trial, they were told to stop after a different amount of time - 3, 6, 9, 12, 15 or 18 seconds, known as a retention interval. After this, they were asked to stop counting and to repeat the trigram, and the percentage of trigrams correctly recalled was recorded for each retention interval.
Findings - The longer the interval delay, the less trigrams were recalled. Participants were able to recall 80% of trigrams after a 3 second delay, but after 18 seconds less than 10% of trigrams were recalled correctly
Conclusion - Information must be rehearsed to keep it in the STM, and it has a limited duration up to 18 seconds, when rehearsal is prevented. The results of this study also show that the STM differs from the LTM in duration
Evaluation - A limitation of this is that the stimulus material was artificial, as trying to memorise consonant syllables does not reflect most real-life memory activities, where what we try to remember is meaningful; may lack ecological validity, but often we do try to remember fairly meaningless things such as phone numbers, so the study is not totally irrelevant.
Duration of the LTM
Depends on the individuals’ lifespan, as memories can last for a lifetime, with items that are originally well coded and contain certain LTMs having longer duration, like those based on skill rather than fact. Information does not have to be consistently rehearsed to retain it, making it different to STM.
- Evidenced by Bahrick et al (1975)
- Goldman and Seamon (1992) asked participants to identify odours of everyday products experienced in the last two years and odours not experienced since childhood, and although identification by name was better for more recent odours, there was significant identification of less-recent odours, suggesting that duration of olfactory information of LTM is very long-lasting
Evaluation -
- Sometimes information in the LTM appears to be lost, but there may simply be a problem of accessing information rather than it not being there
- The type of testing techniques used may affect findings from studies of LTM, and recall is often better when asking participants to recognise stimuli, rather than getting them to recall stimuli
Duration of the LTM - Bahrick et al (1975)
Aim - To investigate the duration of the LTM
Procedure - Participants were given an opportunity sample of 392 American ex-high school students aged 17-74 years. High school yearbooks were obtained from the participants directly or from schools, and recall was tested in various ways including a free recall test, where participants recalled the names of as many of their former classmates as possible, and a photo recognition test where they were asked to identify former classmates from a set of 50 where some were from their yearbook and some weren’t.
Findings - participants who were tested within 15 years of their graduation were about 90% accurate in photo recognition and 60% accurate in the free recall (suggests the strength of triggered LTM), whereas after 48 years, recall declined to 70% on photo recognition and 30% in free recall.
Conclusion - LTM has a seemingly unlimited duration
Evaluation - this study has higher external validity as real-life memories were studied, as when studies on LTM have used meaningless pictures, recall rates were lower, but the downside of this ecologically valid studies is the risk of confounding variables are not controlled, such as participants having looked at yearbook pictures and rehearsed their LTM
Coding in the STM - Acoustic
Information arrives from the SR in its original raw form, such as in sounds or vision, which is then encoded in a form the STM can more easily deal with, and this coding is done in several ways:
1. Visually - thinking of an image
2. Acoustically - repeating a sound / memorising a sound
3. Semantically - through meanings by using knowledge
- Research suggests that STM mainly codes acoustically (by sound) but other codes also exist; sensory codes such as visual are used for stimuli that cannot be remembered acoustically, such as faces or smells
- Baddeley (1966)
- Posner and Keele (1967) found that participants used visual code to assess differences in stimuli, such as recognising a difference in ‘A’ followed by ‘A’ and ‘A’ followed by ‘a’, illustrating how other codes not just acoustic are used in the STM
